You've had the same dentist for 10 years, and have built a wonderful doctor-patient relationship with him. At your last dental examination, he made several recommendations for you to have several teeth root canalled and crowned. Considering you have never had any problems with these teeth, you are not comfortable with his diagnosis.
Every patient has the right to obtain a second opinion, and for that matter, refuse any treatment recommendations that they are not comfortable or willing to go a head with. As long as the patient is capable of making decisions and is of sound mind, the right to a second opinion and the right to refuse treatment stands.
When you choose to obtain a second opinion, and you have found a dentist that you would like to see, the dentist will need to do a complete examination. This examination is required in order for the dentist to record any existing treatment in your mouth, notate the treatment he feels is necessary, and finally, investigate the reason for the second opinion. After the examination has been completed, the dentist will go over his findings with you, and reveal his recommendations. Who you choose to complete the treatment is ultimately your choice.